Heat exchange apparatus



United States Patent [72] Inventors JosephF.Fernandes;

Robert R. Pfouts, Dayton, Ohio [21] Appl. No. 760,776 [22] Filed Sept. 19, 1968 [45] Patented Dec. 1, 1970 [73] Assignee United Aircrafl Products, Inc.

Dayton, Ohio a corporation of Ohio [54] HEAT EXCHANGE APPARATUS 8 Claims, 9 Drawing Figs.

52 us. Cl 165/168; 60/267 [51] Int. Cl F28f3/12 [50] Field of Search 60/260,

[56] References Cited UNITED STATES PATENTS 2,382,218 8/1945 Fernstrurn 165/44X 2,663,142 12/1963 Wilson 60/2'67X 3,240,179 3/1966 Van Ranst 165/44X 2,346,929 4/1944 Litton 165/1 68X 3,409,074 11/1968 Wagner et al 165/134 FOREIGN PATENTS 207,642 12/1923 Great Britain. 376,974 7/1932 -Great Britain.

Primary Examiner-Robert A. OLeary Assistant Examiner-Theophil W. Streule Attorney-J. E. Beringer ABSTRACT: A tubular heat exchanger for use as a surface cooler or the like wherein an array of heat transfer tubes is united into an integral structure and disposed for flow of a ducted fluid over at least one surface thereof, the tube array being useful as a replacement duct section in which it becomes a structural duct component or as a heat exchanger means alone to be disposed intermediately of the duct wall in the path of flowing fluid.

Sheet l 01 2 FIG-l FIG-3 INVENTORS JOSEPH F FERNANDES ROBERT R. PFOUTS THE/R ATTORNEY Patented Dec. 1, 1910 r 3,543,845

Sheet 2 of 2 3 FIG? INVENTOR$ JOSEPH F FERNANDES ROBERT R. PFOUTS THE IR A TTOR/VEY HEAT EXCHANGE APPARATUS This invention relates to heat exchangers, and particularly to surface type coolers or radiators.

An object of the invention is to provide a surface .or like cooler of improved thermal performance and of such simplified construction as to reduce he cost of manufacture thereof.

The term surface cooler is applied to a radiator 'or like device presenting a surface heated by virtue of being in contact with a hot fluid on one side thereof and over which'a rela-'- tively cooler fluid is blown for heat absorption. A wall section of a duct, through which a relatively cool fluid flows, exposed.

on one side to contact with the flowing cool fluid and exposed on the opposite side to a heated fluid, may be regarded as a surface cooler. In the fan bypass duct of a turbofan jet engine,

for example, a surface cooler might utilize the flowing bypass air to cool a lubricating or'hydraulicoil. Asurfacecooler in" such an installation has'an advantage over conventional cooling systems which may require the placing of a plate and fin'or other heat transfer device within the duct and the providing of means to control the flow of both air and. oil therethrough.

The surface cooler may be impractical, however, by reason of relatively low cooling efficiency per unit of area. Heat absorption requirements may be impossibleto achieve, even though principles of extended surface be utilized, without resort to impractically large amounts of surface area.

The instant invention has in view obviating disadvantages of surface coolers of the prior art. There isthus proposed a tubular surface cooler comprised of a plurality of heat transfer tubes joined in an integral structure and lending itself, if desired, to mounting in an air flowingduct as a section thereof. A hot fluid flows through the tubes and is cooled by air flowing over an exposed surface of the tube assembly. The heat exchanger may become a structural component serving the dual functions of complementing the duct configurationand of extracting heat from the hot fluid.'The surface cooler proposed offers distinct advantages over plate and fin and over extended surface coolers since the tubular concept is basically one of prime heat transfer surface. In finned coolers, conditions may be such that the efficiency with which the fins remove heat is low and hence thermal performance can be achieved only with the addition of heat transfer area. The space in which to add such area may at times be unavailable or in other installations the added weight may be undesirable. In the tubular approach, the surface area is basically prime area and hence the heat transfer efficiency is higher.

In accordance with structural concepts of the invention, in an illustrated embodiment thereof, the cooler isconstructed of a row of tubes in staggered array, joined into an integral unit by means inhibiting relative motion between the tubes and precluding fluid flow between and around the tubes. The. tubes are staggered for ease in joining, structural integrity and improved thermal perfonnance. Flanges or other mounting means may be brazed or welded to the tube assembly. Similarly, stiffeners may be added at various longitudinally spaced locations. The ends of the tubes may be suitably manifolded for controlled flow of the hot fluid through the tubes. The parts are suitably united in an integratedform, as.

for example by being nicrobrazed in a dry hydrogen atmosphere. The cooler contour may be straight, arcuate or may assume any other configuration as might be required by a duct in which it is installed as a section thereof. Material selection, tube diameters, tube lengths and like structural characteristics are determined in accordance with each application of the concept.

Other objects and structural details of the invention will appear from the following description, when read in connection with the accompanying drawings, wherein:

FIG. 1 is a plan view of a surface radiator in accordance with an illustrated embodiment of the invention;

FIG. 2 is a view in end elevation of the device of- FIG. 1., shown installed in an annular duct;

FIG. 3 is a view in side elevation of the installed radiator device;

FIG. 4 is a fragmentary detail view in perspective of a core section of the radiator device, an alternate form'of mounting means being shown in connection therewith;

FIG. Stis a fragmentary detail view of a core section as in F IG.'4,.showing an optional use of stiffener. means;

FIG. 6 is a view in side elevation of the core section of FIG.

FIG. 7"isa view of analternate form of heat exchanger, shown in sidetelevation, installed in a fluid flowing duct as a section thereof;

FIG. 8'is a detail view of a header plate useful in connection with manifolding of the tube ends; and

FIG. 9 is a view similar to FIG. 2, showing a form of heat exchangeras there disclosed positioned intermediately of the walls of the annular duct.

Referring to the drawings, there isshown in FIGS. 1 to 3 heat exchangemeans comprisedofa plurality of parallel closely adjacent tubes 10 made of a thin, heat conductive material,'.as for example aluminum or stainless steel alloys. Adjacent tubes are in a side byside, substantially contacting relation and the tube assembly is made into a one-piece, unitary assembly by being subjected to a brazing or like operation. Thus, a plurality of tubes as indicated is put in lateral array in a brazing or like fixture with brazing metal suitably deposited on or between the tubes along the length thereof. At a relatively elevated temperature, in an appropriate environment, the braze metal flows in a manner to fill the joint between adjacent tubes. Upon cooling, the tubes are positively interconnected in a manner to define a seal and a bond therebetween. Nicrobrazing in a dryhydrogen atmosphere may be a mode of uniting the tube assembly into an integral structure. The contour or lateral configuration of the tube assembly is establishedbyuse requirements and is accomplished in the brazingfixture. In'the illustrated instance. the tube assembly has an arcuate configuration. A brazing fixture of this configuration is provided and the tubes loaded and held therein preparatory to and during the brazing operation.

At the tube ends are header plates 11 and 12, a section of one of which is shown in FIG. 8. The header plates are flat metallic sheet members conforming in configuration to that of the tube assembly. Made of a material like that of the tubes 10 in order that they may be joined to the tube ends as part of the same process by which the tubes are joined to one another, the plates have a lateral series of openings 13 therein within which oppositely disposing tube ends are received. Adjacent openings 13 are interconnected by communicating apertures 14. The close fitting tube assembly, in which individual tubes are united: to one another substantially along the lengths thereof, accordingly may. have .its ends received in respective header platesll and l2.with the joint between adjacent tubes being accommodated'in apertures 14.

A recessed housing 15 is attached, as by. welding, to the side of plate 1'1v opposite that receiving tubes 10. A housing 16 is similarly attached to plate 12. The housings l5 and 16, together with'respective plates 11 and I2, constitute manifolding means..The interiors of the respective, housings are in common communication with the ends of tubes 10. Fluid flowing conduits17 and 18 are respectively connected to housings 15 and 16 to communicate with the interiors thereof. The conduits l7 and 18 extend outwardly and vertically of the opposite ends of the heat exchanger construction and terminate in respective vertically displaced flanges l9 and 21. The conduits 1'7 and 18 open through the respective terminal flanges thereof and are adapted to be connected in a fluid flowing system, as for example a system flowing a heated engine lubricating oil in need of cooling. Entering the heat exchanger by way of one of the conduits 17 or 18, the fluid enters a corresponding manifold 15 or 16, distributes itself therein and flows through the tubes 10 to the other manifold housing and out of the heat exchanger by way of its connecting conduit 17 or 18. The heat of the heated fluid is conducted through the tube walls to the exterior thereof to be radiated to ambient surroundings, a process aided by convection flow of a relative ly cooler fluid over at least one of the tube assembly surfaces, as will hereinafter more clearly appear.

The flanges 19 and 21 dispose in a common plane vertically displaced from the assembly of tubes 10. They are apertured for bolting to a supporting surface by which the heat exchanger may be fixed in a relatively projecting relation to such surface. In the illustrated instance of FIGS. 2 and 3, the arrangement provides for mounting of the heat exchanger in an annular air flowing duct 22, as for example the fan bypass duct of a turbofan jet engine. The duct is comprised of inner and outer walls 23 and 24. The outer wall 24 has an opening 25 therein corresponding approximately in outline to the configuration of the instantly disclosed heat exchanger. Installed within the duct 22, the flanges 19 and 21 seat on the interior of inner wall 23 opposite opening 25 and in a manner to project the tube and manifold assembly substantially to be received in and to close such opening. The curvature of the tube and manifold assembly corresponds approximately to the curvature of duct 25. The heat exchanger effectively replaces a section of outer duct wall 24 and becomes in efiect a structural part of the duct. At the same time, a heat transfer surface as represented by the concave side of the assembly of tubes 10 is presented to the duct interior. Air flowing longitudinally through the duct 22, and which is relatively cooler than the heated fluid flowing through the tubes 10, accordingly tends to cool the tube exteriors for a more rapid absorption of heat from the heated fluid passing through the tubes. Desirably, the heated fluid passing through the tubes and the relatively cooler fluid flowing over the tubes are placed in a counterflow relation for maximum heat transfer efficiency. Thus, in orienting the heat exchanger within duct 22, the inlet conduit 17 or 18 is located in a downstream relation tothe flowing duct fluid. Accordingly fluid flowing through the tubes 10 moves counter to the flow of the relatively cooler fluid within the, duct.

The flanges l9 and 21 are detachably secured to inner duct wall 23, as by means of fasteners 26. Openings 27 in the inner duct wall enable conduits 17 and 18 to be connected in a system flowing the heated fluid.

While the conduits 17 and 18, and attached flanges 19 and 21, may provide adequate stability for the heat exchanger, supplemental support means may be used in the form of side brackets 28 and 29. Each bracket 28 and 29 is fastened at a lower end thereof to the inner duct wall 23. An upper end of each bracket is bent to overlap a side portion of the tube assembly and may be united therewith as a part of the brazing process. I

The tubes 10 in assembly define an arcuate section. Individually, the tubes are instaggered array, that is, adjacent tubes are vertically offset from one another. A medial line taken through the tube assembly finds adjacent tubes with their respective axes above and below such line. The arrangement is one to simplify joining of the tubes to one another, to assure a superior structural integrity and to improve thermal performance. A fuller utilization of heat transfer surface is made possible thereby, and, the projection effect achieved by which portions of the present heat transfer surface are thrust upward into the air flow stream, provides an extended surface effect. The tube array may be seen in somewhat greater particularity in FIGS. 4, and 6. Here, the tube array is identical to that of F I68. 1, 2 and 3 but a somewhat modified mounting concept is involved in which flanges 31 (one shown) are mounted to the sides of the tube assembly, again, for example, as a part of the brazing process. Additionally, and as shown in FIGS. 5 and 6, one or more riblike members 32 may be disposed in an underlying relation to the tube assembly to serve as stifi'eners. Each member 32 has a close fitting engagement with an underside of the tube assembly, being formed at longitudinally spaced locations with depressions 33 in which alternate tubes a seat. Intermediate tubes rest on the upper surface of the stiffeners. The arrangement of this form of the invention accordingly is one in which the heat exchanger may be mounted by the flanges 31 to dispose either as a section of a duct, in the manner shown in FIGS. 2 and 3, or simply as an intermediately located heat exchanger in the duct for flow of air over both upper and lower tube assembly surfaces. In the latter instance, stiffeners 32 ordinarily will be omitted, or minimized in order that flow over the tube surfaces will not seriously be restricted.

The manner in which the brazing process forms a fillet 34 between adjacent tubes is clearly illustrated in FIG. 5. The fillet extends lengthwise of the tubes substantially throughout the length thereof and creates between adjacent tubes a bond and seal. Bonding of the tubes to one another in this manner imparts structural integrity to the assembly, preventing vibration and singing," especially when the tube array is intermediately disposed in an air stream with minimum or no support from stiffeners 32. The construction provides a closed face of the tube assembly when the tube array is used as a substituted wall section in the example of FIGS. 2 and 3. Appreciable leakage from the duct is prevented.

In that form of the invention shown in FIG. 7 a plurality of tubes 35 is used which are identical to the tubes 10 and la except that terminal portions of the tubes are bent downward out of the general plane of the tube assembly. The arrangement is one to adapt the heat exchanger for use in an installation wherein it is desirable to present heat transfer surface for contact with the flowing fluid without incurring whatever loss of effect may be involved in locating manifolding means within the fluid duct. Thus, a duct 36 is provided through which a cooling fluid flows under pressure. An opening 37 in the duct is substantially closed by introduction therein of a row of interconnected tubes 35. The tubes 35 are oriented so that the bent over ends thereof dispose outside the duct 36 while intermediate tube portions are substantially received within the opening 37 to form a section of duct 36 and to have the interior air flowing therethrough to sweep over the exposed tube surfaces. The tube assembly may be mounted to the duct in any suitable manner, as for example by brackets 38 and 39 mounted to the exterior of the duct and engaging the tube ends. Also attached to the tube ends are manifolds 41 and 42 by which heated fluid is brought to the tubes 35 for flow therethrough and is conducted therefrom. Intermediate portions of the tube 35 provide a complementary wall surface in the duct 36 with portions of the tube structure projecting by virtue of the staggered tube array into the duct as extended heat transfer surface.

FIG. 9 illustrates an intermediately disposed heat exchanger as heretofore discussed, the construction and arrangement of parts being substantially as shown in FIGS. 2 and 3. In this instance, however, an annular duct 43 in closed. A curved heat exchanger 44 is positioned therein intermediately of the walls of the duct for flow over the heat exchanger on both sides of tubes 45 mounted in manifolds 46. Conduits 47 (not shown) position the heat exchanger 44 between the walls and provide for circulation of a fluid to and from the heat exchanger, as before described. Additional stability is furnished by side brackets 48 and 49. The heat exchanger 44 is securely held within the duct and positioned intermediately for flow lengthwise of the tubes 45 on both upper and lower surfaces thereof.

Manifolding means of any suitable kind may be used in connection with any of the illustrated embodiments. It is not intended, moreover, that structural details illustrated and described should have a limiting effect since it is clear that alternate construction forms and other uses of the invention exist or are possible within the spirit and intent of the inventive concept.

Mounted either as a wall section or as a device intermediately disposed for flow on both sides thereof, the present heat exchanger offers distinct aerodynamic advantages. It achieves desired heat transfer results with no need for special ducting, and, offers minimal obstruction to coolant flow. An important aspect of the invention accordingly is an ability of the cooler to function effectively without materially impeding flow of the fluid to which heat is rejected and without undue use of pressure drop in such fluid.

Individual tubes of the tube assembly may be dimpled, or otherwise deformed, to increase overall therrnalconductance. Velocity-turbulence effects gained thereby specifically improve film coefficients of heat transfer.

In general, preferred embodiments of the invention have been disclosed but it is intended that the scope of the invention should be limited only by the claims allowed herein.

We claim:

1. A tubular heat exchanger, including a row of heat transfer tubes joined into a one-piece integral structure substantially contoured in complementary relation to an opening in a fluid flowing duct, the heat exchanger disposing in the opening and substantially coextensive therewith, one side of said row of tubes being exposed to the duct interior for flow of a fluid over the surface thereof, and manifolding means on the ends of said tubes providing for flow of another fluid through said tubes, said other fluid having a temperature different from the temperature of the fluid flowing through the duct and being in direct heat transfer relation thereto through the walls of said tubes, the tubes being round in cross section with ad jacent tubes of the row being in staggered offset relation to one another and bonded together in substantial line contact by joints substantially coextensive with the tubes to form a unitary, closed core, a major circumferential area of each tube being exposed for direct contact with the first said fluid.

2. A tubular heat exchanger according to claim 1, characterized by tube sheets contoured to agree with the contour of said tube row and having staggered intercommunicating openings therein corresponding to the offset tube arrangement, opposite ends of the tubes being received in the openings of respective tube sheets, closure means mounted to said tube sheets having openings therein and with said tube sheets forming said manifolding means.

3. A tubular heat exchanger according to claim 2, characterized by fluid conducting conduits received at their one ends in said opening in said closure means and terminating at their opposite ends in attachment means by which the heat exchanger may be fixed in position in said duct.

4. A tubular heat exchanger according to claim 1, characterized in that the ends of said tubes are deflected out of the plane of intermediate tube portions to enable said intermediate portions to be exposed to contact with interior duct fluid while ends of the tubes extend outside the duct for attachment to said manifolding means and connection in a system flowing said other fluid.

5. A tubular heat exchanger for use as a surface cooler or the like, including a row of separate substantially straight wall heat transfer tubes in side by side parallel relation, said tubes being round in cross section, means for joining adjacent tubes to one another in substantial line contact, said means acting as a seal and a bond whereby to form an integral row array in which flow around and between adjacent tubes is prevented, said joining means being substantially coextensive with tube length and contacting respective tubes along relatively narrow longitudinal portions whereby to leave major circumferential areas thereof on both sides of said narrow longitudinal portions for heat transfer, manifold means at ends of the tube array providing for flow of a first fluid through said tubes, and means for disposing the heat exchanger in a stream of a second fluid different in temperature from said first fluid for flow of said second fluid over at least one exterior surface of said tube array.

6. A tubular heat exchanger according to claim 5, characterized in that said tube array is comprised of tubes in staggered offset relation to one another, said tubes being alternately raised and lowered relative to a medial horizontal plane, adjacent tubes contacting one another and being united in said plane.

7. A tubular heat exchanger according to claim 5, characterized in that said heat exchanger is disposed in a duct flowing said second fluid therethrough, the tube array being substituted in the wall of said duct as a section thereof exposing an exterior surface for flow of said second fluid thereover.

8. A tubular heat exchanger according to claim 5, characterized in that said heat exchanger is disposed in a duct flowing said second fluid therethrough, the tube array being mounted to dispose between walls of said duct exposing both opposing exterior surfaces thereof to flow of said second fluid thereover. 

